HARVARD University researchers have conducted test flights of miniature robotic insects inspired by the anatomy of a fly.

The robots, which weigh about 80 milligrams, flap their wings 120 times per second to propel themselves into the air.

The researchers believe the robots could eventually be used for crop pollination and search and rescue operations.

RoboBee in flight.

Details of the RoboBee project were published on Friday by the US academic journal Science. The robots took more than 12 years to develop.

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Monash University swarm robotics expert Jan Carlo Barca said in future miniature robots could have many uses, including helping surgeons with operations.

"You could use them for surgery or to find blood clots or cancerous cells," he said. "You can send these robots into very small openings when you do search and rescue and you could use them for environmental monitoring."

The Harvard researchers attached tiny cables to power the robots, which are controlled by a computer. The researchers were unable to find a power source small enough to fit directly onto the robots to let them fly independently.

Video posted on the Harvard website shows a robot, which has a three centimetre wingspan, buzzing in the air for about 10 seconds before crashing to land. Its two wings can flap independently at different speeds.

The robots were made from materials cut by laser that were layered upon one another. They can also fly small distances from side-to-side.

Harvard graduate student Kevin Ma said researchers could now build robot prototypes rapidly and had produced 20 of them in the past six months.

But Dr Barca said there were still many challenges in developing robotic insects. "One problem with very small flying robots is gusts of wind. It's very hard to control."

John Hopkins University researchers have also studied insects to reproduce their flying techniques. The university reported last year that US defence agencies had funded its research.

Dr Barco said the Israel Defence Forces were also developing robotic mosquitoes.